In LTE (Long Term Evolution) cellular systems, as set forth in the LTE specifications of the 3rd Generation Partnership Project (3GPP), a terminal (where a terminal is referred to in LTE systems as user equipment or UE) acquires cellular network access by connecting to a public land mobile network (PLMN) belonging to an operator or service provider. The connectivity to the PLMN is provided by a base station (referred in LTE systems as an evolved Node B or eNB). In addition to such cellular network access, so-called dual-mode UEs also incorporate functionality for simultaneously acquiring network access via a wireless local area network (WLAN), typically WiFi. In a roaming situation, where the UE acquires cellular network access from an operator other than its home operator, the dual-mode UE has choices in routing IP (internet protocol) flows through either the cellular network or one or more WLANs. The home operator (referred to as the home PLMN or HPLMN) may have preferences in this regard as may the visited operator (referred to as the visited PLMN or VPLMN).
The current 3GPP specifications describe the order and priority between HPLMN and VPLMN preferences in different roaming scenarios as being based on two fundamental architectural principles that should be fulfilled: (a) The HPLMN controls the serving PLMN selected by the UE, and (b) in case of conflicts the policies provided by the VPLMN take precedence over the ones provided by the HPLMN. The first principle gives the home operator priority in selecting cellular access, and the second principle is based on the assumption that the VPLMN should have the final say on WLAN network selection for inbound roamers since they are using the VPLMN resources.